Tethering is when a device that already has a network connection shares it with a device that does not. The sharing device acts as a small gateway, passing data to and from the network on behalf of the other device. When a smartphone does this, it is offering a personal hotspot, and the device that joins can reach the internet even though it has no internet connection of its own.
Tethering is switched on in the phone's settings, and that creates the hotspot. On the second device you switch on Wi-Fi or Bluetooth and connect, choosing the hotspot's name and typing the password shown on the phone; Bluetooth devices are paired instead. The phone then uses its mobile data network and passes data between that network and your device.
For example, imagine taking a handheld games console to a park with no Wi-Fi. Your phone has a mobile data plan, so you turn on its hotspot; the console connects and you can play online, because every request travels out through the phone's mobile data connection and the reply comes back the same way.
Tethering does not have to be wireless. A USB cable can carry the shared connection, and it charges the phone while it works, which suits a single device that needs a steady link.
| Method | How the devices link | When it suits you |
|---|---|---|
| Wi-Fi | Second device joins the hotspot by name and password | Several devices need the connection at once |
| Bluetooth | Devices are paired first | Short range, low power, small amounts of data |
| USB cable | One device is plugged into the phone | You want a steadier link and a charging phone |
Staff often work away from the building, where there is no fixed network to join. At a district athletics competition, a teacher recording results on a tablet can tether it to a phone and still add each result to the school's online sports database, because the phone's mobile data connection carries the traffic to the internet and on to that service. Unlike public open Wi-Fi, a hotspot shares mobile data that you control.
Pearson BTEC Digital Information Technology · Communication technologies